The present invention relates generally to electrical shielded connectors terminating a cable assembly of twisted and shielded pairs of conductors, and relates more particularly to an electrical connector without geometrical discontinuity for transmitting very high frequency data signals.
In data transmission networks there are several problems when data is transmitted at high frequency over a plurality of circuits over multi-pair shielded data communication cable. In particular, at high transmission rates, one of the problems is that each wiring circuit itself both transmits and receives electromagnetic signals so that the signals flowing through one circuit or wire pair may couple with the signals flowing through another circuit or wire pair. The unintended electromagnetic coupling of signals between different pairs of conductors of different electrical circuits is called cross-talk, and is a source of interference that often adversely affects the processing of these signals.
Another problem is that the connecting hardware may introduce a geometrical discontinuity in the transmission line geometry of the cabling system. The geometrical parameters of a multi-pair shielded data communication cable such as conductor diameter, insulation thickness, or shield structure, in turn determine the electrical transmission parameters such as impedance, return loss, velocity factor, and so forth.
Today, connectors are designed to provide good electrical performance up to frequencies of about 600 MHz, to be practical to implement on-site, and to maintain continuity between the connector housing and the cable shield. In this vein, U.S. Pat. No. 6,077,122 relates to an electrical connector including an electrically conductive strain relief device that comprises mirrored strain relief members which are in electrical communication with the shield housing and the cable ground path between the cable ground and the contact shield housing. However, the geometry of the connecting system is entirely different from the cable geometry since, in the connecting system, the conductors of the pairs included in the cable are aligned in a plane. Such a geometrical discontinuity generates a discontinuity in the transmission parameters, which results in undesired reflections that modify the attenuation and the return loss of the connector as the frequency approaches 1,200 MHz.
Accordingly, an object of the invention is to provide an electrical connector that preserves the geometrical continuity of the transmission line in order to transmit data signals with frequencies significantly higher than 600 MHz, for example 1,200 MHz.
The invention relates therefore to a connector designed to be interconnected to another connector of the same type to connect two cables. Each cable contains at least one twisted pair for the transmission of very high-frequency differential data signals, in which the conductors of the pair are connected in a connection block by means of Insulation Displacement Contacts (IDC) to contact blades, adapted to ensure contact in an interface block with the corresponding contact blades of the other connector. When the connection is made, the geometry of the elements comprising the connection block is the same as the geometry of the elements comprising the interface block, the geometry being adapted so that the differential mode impedance between the conductors of each pair and the common mode impedance between the conductors and the shielding of the pair are respectively equal to the differential mode impedance between the contact blades and the common mode impedance between the contact blades and the shielding of the connector.